1. Field of the Invention
The present invention relates to an information storage medium, and more particularly, to an information storage medium, such as an optical disk, a recording/reproducing apparatus therefore, and a recording/reproducing method for providing efficient defect management of an information storage medium, including data replacement by logical overwrite (LOW) and data replacement by defect.
2. Related Art
For rewritable information storage media, a spare area is typically provided in a data area for defect management. That is, if a defect is detected while user data is being recorded in a user data area (an area in the data area that excludes the spare area), or while user data recorded in the user data area is being reproduced, replacement data for replacing defect data is recorded in the spare area.
For write-once information storage media, the above defect management technique is used in a logical overwrite (LOW). LOW is known as a method in which write-once information storage media can be used in the same manner as the rewritable information storage media. That is, to update data previously recorded in the user data area, recorded data can be considered as defect data, and data to replace the recorded data can be recorded in the spare area by treating the recorded data as defect data. This makes data management easier since a host can access data using a logical address thereof and data for replacing the recorded data in the user data area can be overwritten at the same location by using the fixed logical address of the data recorded in the user data area and assigning a physical address corresponding to the fixed logical address to the data recorded in the spare area.
Furthermore, a new method which implements LOW for defect management has been suggested to maximize the use of an information storage medium. In such a method, updated data can also be recorded in a non-recorded portion of a user data area, or a spare area on an information storage medium, and replacement information (replacement entry information) can be prepared accordingly.
Data updating by replacement by LOW and replacement by defect will now be described with reference to FIGS. 1A to 1D as follows.
FIG. 1A is an illustrative diagram of an example data area on an information storage medium used to illustrate data replacement when a logical overwrite (LOW) is implemented for defect management.
Referring to FIG. 1A, a data area 100 includes a user data area 110 and at least one spare area 120. Data is typically recorded from a start address of the user data area 110. As shown in FIG. 1A, when data blocks A1, A2, and A3 which have been already recorded at physical locations P1, P2, and P3 in the user data area 110 on an information storage medium, respectively, are to be updated, a host commands a drive system to record data blocks B1, B2, and B3 at the original locations P1, P2, and P3 so as to update the data blocks A1, A2, and A3 to the data blocks B1, B2, and B3 by LOW. The drive system records the data blocks B1, B2, and B3 at physical locations P4, P5, and P6 in the user data area 110 on the information storage medium, and generates a defect list (DFL) entry 130 indicating that the original locations P1, P2, and P3 have been replaced with the replacement locations P4, P5, and P6, as shown in FIG. 1B.
Thereafter, if the host commands the drive system to reproduce the data blocks B1, B2, and B3 from logical addresses corresponding to the original locations, the drive system reproduces the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6 by referring to the DFL entry 130, and transmits the reproduced data blocks B1, B2, and B3 to the host. When the drive system cannot reproduce the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6, data recorded at the replacement locations cannot be guaranteed to be the same as the data recorded at the original locations since the replacement locations P4, P5, and P6 are located in the user data area 110. As a result, the drive system continuously retries to reproduce the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6, and if the drive system fails to reproduce the data blocks B1, B2, and B3, the drive system informs the host that the data blocks B1, B2, and B3 cannot be reproduced.
FIG. 1C is an illustrative diagram of an example data area on an information storage medium used to illustrate conventional replacement by defect.
Referring to FIG. 1C, a data area 100 also includes a user data area 110 and at least one spare area 120. Data is also recorded from a start address of the user data area 110. As shown in FIG. 1C, when a host commands a drive system to record data blocks A1, A2, and A3 at logical addresses corresponding to original locations P1, P2, and P3 in the user data area 110 on an information storage medium, respectively, the drive system detects a defect at the physical location P2 while recording the data blocks A1, A2, and A3 at the physical locations P1, P2, and P3, records the data block A2 at a replacement location Ps in the spare area 120 on the information storage medium by replacing the original location P2 with the replacement location Ps, and generates a defect list (DFL) entry 130 indicating that the original location P2 was replaced with the replacement location Ps, as shown in FIG. 1D.
Thereafter, if the host commands the drive system to reproduce the data block A2 at the logical address corresponding to the original location P2, the drive system reproduces the data block A2 recorded at the replacement location Ps by referring to the DFL entry 130, and transmits the reproduced data block A2 to the host. If the drive system cannot reproduce the data block A2 recorded at the replacement location Ps due to a defect, the drive system can consider the data block A2 recorded at the original location P2 as being the same as the data block A2 recorded at the replacement location Ps since Ps is the replacement location in the spare area 120, as shown in FIG. 1C. As a result, even if the drive system cannot reproduce the data block A2 recorded at the replacement location Ps, the drive system can try to reproduce the data block A2 recorded at the original location P2. If the data block A2 recorded at the original location P2 is error-correctable, the drive system can transmit the error-corrected data block A2 to the host.
In order to maximize utilization of disk capacity and manage information recording media by discriminating between replacement by LOW and replacement by defect, techniques to discriminate between an area for replacement by LOW and an area for replacement by defect have been developed. In one of these techniques, an area for replacement by defect is limited to a spare area allocated for conventional replacement by defect, as shown, for example, in FIG. 1C, and an area for replacement by LOW is limited to a user data area of a data area or a specific area of the user data area, except the spare area, as shown, for example, in FIG. 1A. Thus, whether data at a replacement location has been recorded by replacement by LOW or by replacement by defect can be determined by confirming an area in which the replacement location of a DFL entry (also known as a replacement entry, a defect entry, or a defect/replacement entry) exists.
For write-once information storage media, user data of a replacement block after replacement by defect is the same as user data of an original block before the replacement by defect. However, since the replacement by LOW is mainly used to update data, there is no guarantee that user data of a replacement block be the same as user data of an original block before the replacement by LOW. If a replacement block indicated by a DFL entry is located in a spare area, there is a perception that the DFL entry has been generated due to a defect. Accordingly, user data of an original block can be regarded as being the same as user data of the replacement block. Thus, if the replacement block cannot be error-corrected due to a defect when it is reproduced, the user data can be obtained by reproducing the original block indicated by the DFL entry. More specifically, even if the original block cannot be error-corrected since the original block has been replaced due to the defect, the original block may be sometimes error-corrected by cleaning the dust from a recording surface of an information storage medium.
In this situation, the replacement by defect and the replacement by LOW are discriminated from each other to determine whether user data of a replacement block is the same as user data of an original block by recognizing areas in which replacement blocks of the DFL entry for the two type of replacements are recorded.
However, if a defect occurs during the replacement by LOW, a replacement block by LOW in which the defect occurs should be replaced again. That is, an original block can initially be replaced with a replacement block via replacement by LOW, and then can finally be replaced with a replacement block in a spare area via replacement by defect. As a result of this process, user data of the original block is not the same as user data of the final replacement block due to the intermediate replacement by LOW. Thus, even if a replacement block exists in a spare area, there is no guarantee that user data of the replacement block be the same as user data of the original block.
Accordingly, there is a need to ensure that user data of a replacement block is the same as user data of an original block so as to maximize data usage and increase data reproduction efficiency.